Experimental and numerical study on the auto-ignition of pressurized syngas leakage through a tube

Integrated experimental and numerical investigations are conducted to examine tube-leakage-induced auto-ignition of H2/CO syngas. Experimental results demonstrate that increasing the CO mole fraction significantly reduces the shock wave intensity during leakage while elevating the required ignition pressure. Notably, auto-ignition is observed at CO mole fractions up to 30 % under sufficiently high syngas-air pressure ratios. For all tested compositions, the theoretical shock Mach number remains near 3.5 at critical auto-ignition conditions. Numerical simulations indicate that syngas composition influences leakage auto-ignition primarily through shock intensity rather than chemical reactivity. A prediction method for the critical auto-ignition pressure of hydrogen-rich gas leakage is proposed. This method uses experimental data to correlate average molecular weight with theoretical critical shock Mach number, enabling the generalization of critical leakage auto-ignition pressures across different gas mixtures. Validation against current and previous unobstructed straight-tube experiments confirms the reliability of this method. This framework provides fundamental insights for risk assessment and the safe operation of syngas systems.